CA1153371A - Process for the preparation of 9-hydrazono- 6,7,8,9-tetrahydro-4h-pyro[1,2-alpyrimidine -4-one compounds, the salts and hydrates thereof, certain representatives of the compound prepared and pharmaceutical compositions containing them - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The invention provides a process for the preparation of a nitrogen bridgehead compound of the formula I
wherein R1 is hydrogen, lower alkyl, styryl, or lower alkoxycarbonyl; R2 is hydrogen or lower alkyl; R3 is carboxy, lower alkoxycarbonyl, carbamoyl, cyano, formyl, or lower alkyl; R4 is hydrogen, lower alkyl, hydroxyethyl, carboxy-lower alkyl, methoxycarbonyl, ethoxycarbonyl, trifluoromethyl, benzyl, 2-, 3- or 4-pyridyl, or benzothiazol-2-yl, phenyl or naphthyl or phenyl or naphthyl substituted by at least one of hydroxy, halogen, lower alkyl, sulfo, carboxy, lower alkoxy, methylenedioxy, amino, nitro and tri-fluoromethyl; R5 is hydrogen, lower alkanoyl, benzoyl or nicotinoyl or the group -NR4R5 is piperidinyl, pyrrolidinyl or morpholinyl, or a pharmaceuti-cally acceptable salt, hydrate, stereoisomer, optically active isomer, geo-metric isomer or tautomer thereof, which comprises reacting a racemic or optically active compound of the formula II

wherein X is halogen, with a compound of the formula III

Description

1` ~15;3371 : The presi~nt invi3ntion relates to a prociJss ror thi i,rei)aratiorl oE
9-hydrazono-6,7,8,9--tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one compounds, the salts and hydrates thereof. The compounds possess interesting physio-logical properties particularly antiallergic ancl/or ant:iasthmatic propert.ies.
It is well known that certain pyridoL:L,2-a~pyrim:icline derivatives possess analgesic and CNS influencing ac-tivity (British Patent Speci:c:i.cation Serial No. 1,209,946). One of the most preferred representatives of these : compounds is 3-(ethoxycarbonyl)-1,6-dimethyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[l,2-a]pyrimidinium methosulfate (PROBO~ , Rimazolium) ~Arzneimittel Forschung, 22 [1972] 815) which is widely used in the clinical practice as analgetic. Pyrido[1,2-a]pyrimidine derivatives are prepared from the cor-responding (2-pyridylamino-methylene)-malonic acid dialkyl esters by ring closure. Further substituted pyrido[l,2-a]pyrimidine compounds are disclosed in the British Patent Specification Serial No. 1,454,312.
. According to one feature of the present invention there is provided a new process for the preparation of compounds of the general formula R \ / R

: N
. N N R
1 ~ ~ R3 R O

wherein R represents hydrogen, lower alkyl, styryl or lower alkoxycarbonyl R represents hydrogen or lower alkyl; R represents carboxy, lower alkoxy-. 20 carbonyl, carbamoyl, cyano, formyl or lower alkyl; R represents hydrogen, lower alkyl, hydroxyethyl, carboxy-lower alkyl, methoxycarbonyl, ethoxy-: carbonyl, trifluoromethyl, benzyl, 2-, 3- or 4-pyridyl, or benzothiazol-2-yl, . phenyl or naphthyl or phenyl or naphthyl substituted by at least one of hydroxy, halogen, lower alkyl, sulfo, carboxy, lower alkoxy, methylenedioxy, amino, nitro and trifluoromethyl; R represents hydrogen, lower alkanoyl, benzoyl or nicotinoyl; or R and R together with the nitrogen therebet.ween ..~
'''' '3~
:;; ~
.~i - 1 -~53371 represent a piperidinyl, pyrrolidinyl or morphoLLnyl cJroup.
The term "lower alkyl" used herein for alkyl cJroups or alkyl con-taining groups, such as alkoxy groups, generally stands for C1 6' preferably Cl 4 straight or branched chained aliphatic satura-ted hydrocar~orls, such ~s methyl, ethyl, n-propyl, isopropyl, n-bu-tyl, seeoncdary butyl, tertiary butyl, n-pentyl, neo-pentyl, n-hexyl etc.
Preferred compounds prepared according to the present invention in-clude compounds of the general formula I, wherein R represents hydrogen, - methyl, styryl or methoxyearbonyl or ethoxyearbonyli R represents hydrogen 10 or methyli R represents carboxy, methoxyearbonyl or ethoxyearbonyl, earbam-oyl, eyano, formyl or methyl; Ris hydrogen, methyl, hydroxyethyl, carboxy-lower alkyl, methoxycarbonyl, ethoxyearbonyl, trifluoromethyl, benzyl, 2-, 3-or 4-pyridyl, or benzothiazol-2-yl, phenyl or naphthyl or phenyl or naphthyl substituted by at least one of hydroxy, halogen, lower alkyl, sulfo, carboxy, lower alkoxy, methylenedioxy, amino, nitro and trifluoromethyl; R representS
hydrogen, aeetyl, benzoyl or nieotinoyl; or the group -NRR stands for piperidinyl, pyrrolidinyl or morpholinyl. R preferably represen-ts phenyl, bearing optionally one, two or three substituents in o-, m- and/or p-position, seleeted from hydroxy, halogen, lower alkyl, sulfonie acid, carboxy, lower 20 alkoxy, methylenedioxy, amino, nitro and trifluoromethyl.
An especially preferred class of compounds of the general formula I
ineludes those eompounds, in whieh R is 6-methyl, R is hydrosen, R stands ; for earboxy, R stands for optionally substituted phenyl, R is hydrogen and pharmaeeutieally aceeptable salts thereof.
The eompounds of the general formula I form salts with pharmaeeuti-;~ cally aceeptable organie and inorganie aeids. Hydrochlorides, hydrobromides, hydroiodides, sulfates, nitrates, phosphates, maleates, malates, succinates, acetates, tartarates, lacta-tes, fumarates, citrates, etc. may for example be formed.
30 Compounds of the general formula I containing carboxy or sulfonic ;.
acid groups form salts with pharmaceutically acceptable bases, such as alkali metal salts, e.g. sodium or potassium salts; alkali earth metal salts, ;~ - 2 -.~ , l~S3371 e.g. calcium or magnesium salts, ammonium salts; and with organi.c amines, such as triethylamine salts, ethanol amine sal-ts, etc.
The invention provides optical and geometrical isomers and tauto-: mers of the compounds of the general formula I as well. The structure o:E
geometric isomers is shown by the formulae R4 \ N
~ N ~ R IA

; ~ ~ R
Rl O

and R
/

/ \ 4 N R
N ~ IB
~ N

R O
The structure of the tautomers is shown by reaction scheme A:

N
I N N
:. NH l ll N N

~ ~ R ~ ~ 1 ;~ Rl O R O

According to the invention the compounds of the general formula I, pharmaceutically acceptable salts thereof, hydrates, optically active, geo-metric and stereoisomers and tautomers thereof are prepared by reacting a compound of the general formula ~ 3 -,, ~ ~ ' , ~` :

1~53371 ~ ~ N ~ R II
1 ~ ~ R3 wherein R , R and R are as hereinbefore defined and X represents halogen, with a compound oE the general formula N III

wherein R and R are as defined hereinabove.
In the compounds of the general formula II used starting materials X preferably stands for ''';
,' ,`, ¢
~, .

, ~

~53371 chlorine, brcmine ox iodine. The compound of the ~n~ral formula III is pre-ferably used in an amount of 1 to 3 molar equivalent. me reaction of oom~
pounds of the general formulae II and III may preferably be conducted in the presence of an acid binding agent. As acid binding agents preferably alkali metal carbonates, such as sodium or potassium carbonate, alkali metal hydrogen carbonates, such as sodium or potassium hydrcgen carbanate, alkali metal salts of weak acids, such as sodium acetate or an excess or the start-ing material of the general formula III may be employed. me reaction can - optionally be carried out in an inert solvent. AS reaction medium pxeferably aromatic hydrocarbons, such as benzene, toluene, xylene; esters, such as ethyl acetate; alcohols, such as methanol, ethanol; dimethyl formamide;
dimethyl sulfoxide; or halogen containing hydrocarbons, such as chloroform, dichloroethane, chlorobenzene can be used.
me reaction is performed at a temperature of 0 to 200 &, prefer-ably at room temperature or at the boiling temperature of the reaction mix-ture.
The compcunds of the general formuha I obtained can be isolated ~ fm m the reaction ,',' ".'~
.

.
~' ..

. - 5 -`~ X!
'' 1~5~3371 mix-ture by methods kno~n per se. In m~lny cases the compouncl oE the general formula I or a salt or hydrate thereof precipitates from the reaction mixture and can be eliminated by filtration or centrifuging. If the product does not precipitate from the reaction mixture, it can be preeipitated with ar,other solvent, for example water, methanol, or can be lsolated by clistilling of~
the organie solvent. The eompounds of the general formula I obtained, if required, ean be purified by reerystallization, ehromatography or boiling with a suitable solvent.
Compounds of the general formula I having a different group from hydrogen in plaee of R contain a centre of asymmetry. ~he optically active antipodes of the compounds of the general formula I can be prepared by starting from optically active compounds of the general formula II.
Starting compounds of the general formula II, wherein R , R , R
` and X are as hereinbefore defined can be prepared from compounds of the general formula ,~ ~ N ~ R IV

~ N

R

,.~

' . . .
r ' ''''~

d ~5~37~
wherein Rl, R2, and R are as hereinbefore defined, by halogenation (Arzneimittel Forschung 22, /1972/ 815). As a halogenating agent elementary halogen, such as brcmine; an acid halide, such as sulfuryl chloride; organic halogene derivatives, such as N-brcmo-succinimide, ete. can be used. The reaction is conducted in an organic solvent, preferably at room temperature, optionally in the presen oe of an acid binding agent, for example sodium ace-tate.
The allergic reactions induced by the antigen-antibody interaction may occur in the different tissues and organs accompanied by different symptoms. m e most frequent form of the allergy is asthma. As antiasthmatic agent disodium chromoglycate [1,3-bis-(2-carboxychrcmon-6-yl-ox)-2-hydroxy-propane, IntalR] is widely used, but is not active orally and it produces the desired effect only by using an inhaler, which makes administration rather ccmplicated. We have now found that the ccmpounds of the general formLla I
cure the allergic symptoms both orally and intravenously as well as by inhal-' ing.
The efficiency of the co~pounds of the general formula I was proved .
by standard tests to determine antiallergic activity. The test is carried ; out by the PCA test-method (Ovary: J. Immun. 81, 355, 1958) and the Church-; 20 test (British J. Pharm. 46, 56-66, 1972; Immunology 29, 527-534, 1975) and as ccmparing substance disodium chromoglycate is used. The test is carried out on rats. The results obtained in PCA test are summarized in Table I.

''' ,:
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~:~LS3371 ~ Table I

. .
~ PCA test C o m p o u n d ED50 ` ~moler/kg.
' l.v.
-9-(phenylhydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]- 0.60 ; pyrimidine-3-carboxylic acid (+)-9-~nylhydrazono)-6-methyl-4-o~o-6,7,8,9-tetrahydro-4H-pyrido- 0.29 [1,2-a]pyrimidine-3-carboxylic acid 9-(4-ethoxyphenylhydrazono)-6-methyl-: 4-oxo-6,7,8,9-tetrahydro-4H-pyrido- 0.87 [1,2-a]pyrimidine-3-carboxylic acid 9-(2-carboxyphenylhydrazono)-6-methyl-4-oKo-6,7,8,9-tetrahydro-4H-pyrido- 0.48 [1,2-a]pyrimidine-3-carboxylic acid 9-(4-carboxyphenylhydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido- 7.60 .~ [1,2-a]pyrimidine-3-carboxylic acid ~ 6-methyl-9-(3-nitrophenylhydrazono)-; 4-oxo-6,7,8,9-tetrahydro-4H-pyrido- 0.52 [1,2-a]pyrimidine-3-carboxylic acid .~.
s 9-(3-chlorophenylhydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido- 0.61 [1~2-a]pyrimidine-3-carboxylic acid 9-(4-chlorophenylhydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido- 0.53 - [1,2-a]pyrimidine-3-carboxylic acid . .
9-(4-bromDphenylhydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido- 0.82 ; [1,2-a]pyrimidine-3-carboxylic acid , 9-(3-pyridylhydrazono)-6-methyl-4-ox~-i 6,7,8,9-tetrahydro-4H-pyrido[1,2-a]- 0.54 ~ pyrimidine-3-carboxylic acid ~ 6-methyl-9-(3-methylphenyIhydrazono)-.. 4-ox~-6,7,8,9-tetrahydro-4H-pyrido- 0.42 : [1,2-a]pyrimidine-3-carboxylic acid ., Disodium chromoglycate 1.00 The above data show that the representatives of the compounds of the general formLla I exhibit oral activity as well, whereas disodium chromo-,, ~S;~37~
glycate is effective only when administered intravenously. Compounds of the general formula I are more active also when administered i.v.
m e toxicity of the conpounds of the general formula I is low, generally LD50 500 mg./kg. p.o. on rats and mice.
The compounds of the general formula I, in which (a) R stands for araIkyl or halogen and R, R, R, R and R are as herein-before defined, (b) R4 represents the group -(C~12)m-Het (in which n is the integer 1, 2 and 3 and Het stands for an optionally substituted heterocyclic group) and R, R, R, R and R are as hereinbefore defined, except that R and R
~ are not linked; or (c) R5 is Cl 6alkyl or aryl optionally substituted by one or more substitu-; ents, and R, Rl, R2, R3 and R4 are as hereinbefore defined, except that R and R æ e not linked, ` are new.
` m e co~pounds of the general form~la I may be employed in the form of ph æ maoe utical compositions containing the active ingredient in associa-` tion with inert solid or liquid organic or inorganic carriers. m e composi-, tions æ e prep æ ed by methods kncwn per se.
The compositions may be formLlated in a form suitable for oral, parenteral administration or for inspiration, such as tablets, dragées, cap-sules, lozenges, powder mLxtures, aerosol sprays, aqueous suspensions or solu-` tions, injection solutions or syrups. The composition can contain suitable , solid diluents or c æ riers, sterilizing aqueous solvents, ncn-toxic organic ; solvents. To the compositions suitable for oral administration the usual flavouring or sweetening agents can be added.
As carriers for the tablets suitable for oral administration prefer-ably lactose, sodium citrate, calcium carbonate and disintegrating substan oe s,such as starch, sodium lauryl sulfate, magnesium stearate are used. m e carrier of the capsules preferably is lactose of polyethylene glycol. The _ g _ ~5~3371 aqueous suspensions may contain emulsi~yLng and suspendiny agents. For dilu-tion of the organic solvent suspensions ethanol, glycerin, chloroform, etc.
can be used.
The compositions suitable for parenteral administration and inspira-tion æ e solutions or suspensions of the active ingredient in a suitable medium, e.g. peanut sezam oil, polypropylene glycol or water. m e injection compositions may ke administered intramuscularly, intravenously or subcutane-ously. The injection solutions are preferably prepared in an aqueous medium and the pH is adjusted to an appropriate value. m e solutions may ke pre-pared if desired, in the form of phasiological saline or glucose solutions.
`~ m e compositions may be administered also by inhalation when curing asthma, ky using the conventional inhalating and nebulizating equipments.
The active ingredient content of the pharmaceutical compositions may vary within a wide range and may ke 0.005 to 90 %.
The daily effective dose depends on the condition, age and weight of the patient and on type of formulation and activity of the active ingredi-ent. The daily oral dosage level generally lays between 0.05 and 15 g./kg.
; while the daily dosage level generally is 0.001 to 5 mg./kg. at once or in several portions a day when administered intravenously or by inspiration.
m e above data are for orientation only, the exact doses should always ke prescribed by the physician. Alterations in both directions are allowed.
Further details of the invention are illustrated by the follcwing ~ Examples which are given for illustration and not for limitation.
Example 1 0.73 g. (0.002 moles) of 9,9-dibr o-6-methyl-4-oxo-6,7,8,9-tetra-hydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid are dissolved in 2 ml. of dimethyl sulfoxide. To the solution 0.2 ml. (0.002 moles) of phenyl hydrazine and 0.5 ml. (0.004 moles) of N,N-dimethylaniline are added. There-after the reaction mixture is allowed to stand for three days. m e precipit-' 1~l5~337~
ated crystals are filtered off and washed with methanol. The product is puri-fied by alkaline/acidic precipitation. 0.4 g. (64.0 %) of 9-(phenyl-hydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid are obtained, melting at 254 to 255 &.
Analysis for Cl6H16N4O3:
calculated: C 61.53 %, H 5.16 %, N 17.94 %;
found: C 61.42 %, H 5.07 %, N 17.85 %.
Example 2 ., Following the prooedure described in Example 1 but using triethyl amine instead of N,N-dimethylaniline as an acid binding agent, 9-(phenyl-hydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboKylic acid is obtained, melting at 255 to 256 C. Yield: 60.5 %. me product doe s not give any melting point depression when admixed with the pro-duct of Example 1.
; Example 3 4.0 g. (0.01 moles) of 3,9,9-tribrom~-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one are dissolved in lO ml. of dimethyl sul-foxide. To the solution 2.8 ml. (0.03 moles) of phenylhydrazine are added.
me reaction mix*Nre is allcwed to stand for three days whereuFon 20 ml. of water are added. me solvent is decanted from the precipitated substanoe and the product is recrystallized frcm methanol. 1.3 g. (34.7 %) of 3-bromo-9-(phenylhydrazono)-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one are obtained, melting at 190 to 192 &.
Analysis for C15H15N4OBr:
calculated: C 51.89 %, H 4.35 %, N 16.14 %, Br 23.01 %;
found: C 51.77 %, H 4.43 %, N 16.32 %, Br 23.31 %.
Example 4

2.0 g. (0.005 m~les) of 9,9-dibromo-6-methyl-4-oxo-6,7,8,9-tetra-hydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid ethyl ester and 0.9 g.
(0.005 mDles) of piperonylic acid hydrazide are dissol~ed in 80 ml. of ~, .
.

~5;~371 pyridine. The solution is allcwed to stand for two days whereupon the solvent is distilled off in vacuo. To the residue 30 ml. of water are added. After a short standing the crystals are filtered off an~ recrystallized from methanol. 0.5 g. (24.2 ~) of 6-methyl-9-(3,4-methylenedioxybenzoylhydrazono)-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid ethyl ester are obtained, melting at 183 to 185 C.
Analysis for C20H20N4&
calculated: C 58.25 %, H 4.89 %, N 13.59 %;
found: C 57.95 %, H 4.81 %, N 13.42 %.
, 10 Example 5 Following the procedure described in Example 4 but replacing piperonylic acid hydrazide by benzoid acid hydrazide, 9-(benzoylhydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic ad d ethyl ester is obtained, melting at 209 to 210 C. Yield: 24.7 %.
Analysis for ClgH20N4O4:
calculated: C 61.96 %, H 5.47 %, N 15.20 %;
found: C 61.81 %, H 5.39 %, N 15.09 %.
Example 6 To 80 ml. of methanol 11.0 g. (0.03 moles) of 9,9-dibrcmo-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid are added. To the suspension 20 ml. of a 50 % by weight hydrazine hydrate solu-tion is added in one portion, under vigorous stirring. The temperature of the reaction mixture increases and finally a solution is obtained. The solu-tion is stirred at room temperature for two to three hours and the precipit-ated crystals are filtered off. The hydrazinium salts separated by filtra-tion is dissolved in 40 ml. of water and the salt is set free by adding solid potassium hydrogensulfate. me precipitated crystals are filtered off, washed with a small amount of water and dried.
Recrystallization from a 50 % (v/v) aqueous ethanol solution yield 4.0 g. (65.4 %) of 9-hydrazono-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido-[1,2-a]pyrimidine-3-carboxylic acid, melting at 202 to 203 &.

~ 5~371 ~ nalysis for C1oH12N4O3:
calculated: C 50.84 %, H 5.12 %, N 23.72 %;
found: C 50.56 %, H 5.03 %, N 23.57 %.
Examele 7 Into 140 ml. of methanol 18.3 g. (0.05 moles) of 9,9-dibromo-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid and 10.5 ml. (0.2 moles) of methyl hydrazine are added. The reaction mLxture is stirred and allowed to stand for two days. The solvent is distilled off in vacuo. The residue is dissolved in 50 ml. of water and the pH is adjusted to 3 with a 10 % by weight hydrochloride acid solution. The precipitated cry-stals are filtered off, dried and recrystallized from methanol.
; 5.6 g. (44.8 %) of 6-methyl-9-(methylhydrazono)-4-oxo-6,7,8,9-tetra-hydro-4H pyrido[l,2-a]pyrimidine-3-carboxylic acid are obtained, melting at 219 to 220 C.
Analysis for CllH14N403:
calculated: C 52.79 %, H 5.64 ~, N 22.39 %;
found:C 52.61 %, H 5.58 %, N 22.23 %.
Examples 8 to 24 1.83 g. (0.005 moles) of 9,9-dibromo-6-methyl-4-oxo-6,7,8,9-tetra-hydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid are dissolved in 5 ml. of dimethyl sulfoxide. To the solution 0.005 moles of the monohydrochloride of the corresponding hydrazine derivative indicated in Table II and 1.3 ml.
(0.01 moles) of N,N-dimethylaniline are added. me reaction mixture is allcwed to stand at room temperature. The precipitated crystals are filtered off and recrystallized fr~n the solvents given in Table II.
Examples 25 to 39 1.83 g. (0.005 moles) of 9,9-dibromo-6-methyl-4-oxo-6,7,8,9-tetra-hydro-4H-pyrido[1,2-a]pyrimidine-3-cæ~oxylic acid are dissolved in 5 ml. of dimethyl sulfoxide. To the solution 0.015 moles of a hydrazine derivative shcwn in Table III are added. me reaction mixture is allcwed to stand at ~L5~337~
room temperature for three days. rnhe precipita-te crys-tals are filtered off and recrystallized from the solvents listed in Table III.

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Eoiled ~x Instead of (+)-9,9-dibromo-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido-[1,2-a]pyrimidine-3-carboxylic acid optically active (-)-9,9-dibro~o-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid is used.

xxx Instead of racemic (+)-9,9-dibromo-6-methyl-4~oxo-6,7,8,9-tetrahydro-4H-pyrido[l,2-a]pyrimidine-3-carboxylic acid optically active (+)-9,9-di-bromL-6-me~hyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid is used.

:
: .

~5~337~
Example 40 Follcwing the procedure described in Example 25 but replacing 9,9-dibromL-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carbQxylic acid by 9,9-dibrcnl-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido-[1,2-a]pyrimidine-3-carbonitrile and recrystallizing the crude product fram acetomtrile 9-(phenylhydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido-[1,2-a]pyrimidine-3-carbonitrile monohydrate is obtained, melting at 222 to 223 &. Yield 41.7 %.
AnalySi9 for C16H15N5 E2O
calculated: C 61.73 %, E 5.50 %, N 22.49 %;
found: C 61.47 %, H 5.42 %, N 22.67 %.
Example 41 Follcwing the procedure described in Example 25 but replacing 9,9-dibromL-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carbQxylic acid by 9,9-dibromo-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido-[1,2-a]pyrimidine-3-carboxamide and recrystallizing the crude product from nitromethane, 9-(phenylhydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido-[1,2-a]pyrimidine-3-carboxamide is obtained, melting at 246 to 247 C.
Yield: 40.5 %.
Analysis for C16H17N5O2:
calculated: C 61.73 %, H 5.50 %, N 22.49 %;
found: C 61.61 %, H 5.48 %, N 22.40 %.
Example 42 , Follcwing the procedure described in Example 25 but replacing 9,9-dibromo-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid by 9,9-dibrQmo-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]-pyrimidine-3-carboxylic acid, 9-(phenylhydrazono)-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid is obtained, melting at 267 to 268 C. Yield: 41.7 %.

. .. ~

~S~37~

Analysis ~or C15H14N4O3:
calculated: C 60.39 ~, H 4.73 ~, N 18.78 %;
found: C 60.18 %, H 4.71 %, N 18.66 %.
Example 43 , Following the procedure described in Example 25 but replacing 9,9-dibromo-6-methyl-3-cxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-: carboxylic acid by 9,9-di~romo-7i~ethyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido-[1,2-a]pyrimidine-3-carboxylic acid, 9-(phenylhydrazono)-7-methyl-4-oxo-; 6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid is obtained, melting at 260 to 261 &. Yield: 40.1 %.
Analysis for C16H16N4O3:
calculated: C 61.52 %, H 5.16 %, N 17.93 %;
found: C 61.69 %, H 5.07 %, N 18.11 %.
Example 44 Follow m g the procedure described in Example 3 but replacing 3,9,9-tribromo-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one by 9,9-dibromo-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one, 9-(phenylhydrazono)-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one is obtained, melting at 163 to 164 &. Yield: 31.7 %.
Analysis for C15H16N4O:
calculated: C 67.15 %, H 6.01 %, N 20.88 %;
found: C 67.33 %, H 6.09 %, N 20.77 %.
Example 45 Follcwing the prccedure described in Example 3 but replacing 3,9,9-tribromD-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one by 9,9-dibromo-3,6-dimethyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one, 9-(phenylhydrazono)-3,6-dimethyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-; 4-one is obtained, melting at 165 to 166 C.
Analysis for C16H18N4O:
~ 30 calculated: C 68.06 %, H 6.43 %, N 19.84 %;

; found: C 67.81 %, H 6.59 %, N 19.64 %.

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;

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Example 46 1.8 g. ~0.005 moles) of 9,9-dibromo-6-methyl-4-oxo-6,7,8,9-tetra-hydro-4~1-pyrido[1,2-a]pyrimidine-3-carboxylic acid are dissolved in 5 ml. of dimethyl sulfoxide. To the solution 1.8 g. (0.015 moles) of N-phenyl-N-methyl-hydrazine are added. The reaction mixture is allowed to stand for three days, whereupon 10 ml. of water are added. The solvent is decanted from the pre-cipitated substance and the product is crystallized from methanol.
0.8 g. (49.0 %) of 9-(N-phenyl-N-methyl-hydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid are obtained, melting at 196 to 198 C.
Analysis for C17H18N4O3:
calculated: C 62.57 %, H 5.56 %, N 17.17 %;
found: C 62.86 %, H 5.36 %, N 17.33 %.
Example 47 Follcwing the procedure described in Example 3 but replacing 3,9,9-tribromo-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin~-4-one by 9,9-dibrom~-3-ethyl-2,6-dimethyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-; one, 3-ethyl-9-(phenylhydrazono)-2,6-dimethyl-6,7,8,9-te~rahydro-4H-pyrido-;~ [1,2-a]pyrimidine-4-one is obtained, melting at 135 to 137 C. Yield 40.1 %.
Analysis for C18H22N40:
calculated: C 69.65 %, H 7.14 %, N 18.05 ~;
found: C 69.42 %, H 7.09 %, N 18.00 %.
Example 48 Following the procedure described in Example 3 but replacing 3,9,9-tribromo-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one by 9,9-dibromo-3-phenyl-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-4-one, 3-phenyl-9-(phenylhydrazono)-6-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]-pyrimidine-4-one æe obtained, melting at 146 to 148 C. Yield: 45.5 %.
Analysis for C21H20N4O:
calculated: C 73.23 %, H 5.85 %, N 16.27 %;
found: C 73.00 %, H 5.81 %, N 16.22 %.

;
.

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Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of a nitrogen bridgehead compound of the formula I
wherein R1 is hydrogen, lower alkyl, styryl, or lower alkoxycarbonyl; R2 is hydrogen or lower alkyl; R3 is carboxy, lower alkoxycarbonyl, carbamoyl, cyano, formyl, or lower alkyl; R4 is hydrogen, lower alkyl, hydroxyethyl, carboxy-lower alkyl, methoxycarbonyl, ethoxycarbonyl, trifluoromethyl, benzyl, 2-, 3- or 4-pyridyl, or benzothiazol-2-yl, phenyl or naphthyl or phenyl or naphthyl substituted by at least one of hydroxy, halogen, lower alkyl, sulfo, carboxy, lower alkoxy, methylenedioxy, amino, nitro and tri-fluoromethyl; R5 is hydrogen, lower alkanoyl, benzoyl or nicotinoyl or the group -NR4R5 is piperidinyl, pyrrolidinyl or morpholinyl, or a pharmaceuti-cally acceptable salt, hydrate, stereoisomer, optically active isomer, geo-metric isomer or tautomer thereof, which comprises reacting a racemic or optically active compound of the formula II
wherein X is halogen, with a compound of the formula III

or an acid addition salt thereof, at room temperature for a period of from 2 to 3 hours under vigorous stirring to a period of 2 to 3 days, standing, and, if required, converting an obtained salt to the free compound of formula I or converting a compound of formula I into a pharmaceutically acceptable acid addition salt.

2. A process as claimed in claim 1 in which X represents chlorine or bromine.

3. A process as claimed in claim 1 which comprises starting from an optically active compound of the general formula II, in which R1 is other than hydrogen.

4. A process as claimed in claim 1, which comprises using an acid addition salt of a compound of the general formula III in an amount of 1 to 3 molar equivalents related to the amount of the compound of the general formula II employed.

5. A process as claimed in claim 1, which comprises carrying out the reaction in an inert organic solvent, preferably in an alkanol or in a halo-genated hydrocarbon or in an organic acid nitrile.

6. A process as claimed in claim 1 which comprises carrying out the reaction in dimethyl sulfoxide.

7. A process as claimed in claim 1, which comprises carrying out the reaction in the presence of an acid binding agent, preferably tertiary amines or pyridine.